Variable Guide Vane for Gas Turbine Engine

TECHNICAL FIELD

The disclosure relates generally to aircraft engines, and more particularly to variable orientation guide vanes of gas turbine engines.

BACKGROUND

Variable orientation guide vanes, also called variable guide vanes (VGVs), are commonly used in aircraft gas turbine engine compressors and fans, and in some turbine designs. Typically, VGVs have spindles through their rotational axis that penetrate the casing and allow the VGVs to be rotated using an actuation mechanism. VGVs direct air onto rotors of the gas turbine engine at a desired angle of incidence for engine performance and efficiency. In some operating conditions of gas turbine engines, it can be desirable to orient the VGVs at aggressive vane angles. However, the range of motion of VGVs can be limited in existing arrangements of VGVs. Improvement is desirable.

SUMMARY

In one aspect, the disclosure describes a variable orientation guide vane for a gas turbine engine. The variable orientation guide vane comprises:

an airfoil for interacting with a fluid in a gas path of the gas turbine engine, the airfoil having a leading edge and a trailing edge; and

a button, the airfoil being mounted to the button and rotatable with the button about an axis during use, the button having a leading end at an angular position corresponding to an angular position of the leading edge of the airfoil relative to the axis, the button including a platform surface for facing the gas path and defining part of the gas path during use, the platform surface including a depression for receiving therein part of an adjacent variable orientation guide vane, the depression defining a sunken portion of the platform surface that is lower than a leading end portion of the platform surface at or adjacent the leading end of the button.

In another aspect, the disclosure describes a variable guide vane assembly for a gas turbine engine. The assembly comprising:

a shroud including a shroud surface defining a first part of an annular gas path of the gas turbine engine, the shroud including a receptacle defined in the shroud surface;

a first vane rotatably mounted inside the annular gas path, the first vane including a button and a first airfoil mounted to the button, the button being received in the receptacle of the shroud, the first button including a platform surface defining a second part of the annular gas path adjacent the first airfoil, the platform surface including a depression defining a sunken portion of the platform surface; and

a second vane rotatably mounted inside the annular gas path adjacent the first vane, the second vane including a second airfoil, the second vane being rotatable between: a first orientation where a part of the second airfoil of the second vane is outside of the depression in the platform surface of the first vane; and a second orientation where the part of the second airfoil of the second vane is inside the depression in the platform surface of the first vane.

Embodiments may include combinations of the above features.

In a further aspect, the disclosure describes a method of operating adjacent variable orientation first and second vanes disposed in an annular gas path of a gas turbine engine, the first vane having a first button and a first airfoil mounted to the first button, the second vane having a second button and a second airfoil mounted to the second button, the first and second buttons being rotatably disposed in respective receptacles formed in a shroud defining part of the annular gas path, the first button including a platform surface including a depression defining a sunken portion of the platform surface, the method comprising:

rotating the first and second vanes; and

when rotating the first and second vanes, receiving part of the second airfoil of the second vane in the depression formed in the first button of the first vane.

Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings, in which:

FIG. 1 shows an axial cross-section view of an exemplary turboprop gas turbine engine including variable orientation guide vanes as described herein;

FIGS. 2 A and 2 B are schematic representations of a variable orientation guide vane at different angular positions;

FIG. 3 is a tridimensional view of two exemplary adjacent variable orientation guide vanes rotatably mounted in an annular gas path of a gas turbine engine;

FIG. 4 is an enlarged tridimensional view of parts of the variable orientation guide vanes of FIG. 3 ;

FIG. 5 is a schematic side view of one of the variable orientation guide vanes of FIG. 3 together with a shroud surface;

FIG. 6 A is a tridimensional view of an exemplary button of a variable orientation guide vane without a depression formed therein showing a baseline geometry of a platform surface of the button;

FIG. 6 B is a tridimensional view of the button of FIG. 6 A with a depression formed in the platform surface;

FIG. 7 is a schematic top view of the variable orientation guide vane of FIG. 6 B ; and

FIG. 8 is a flowchart of a method of operating variable orientation guide vanes.

DETAILED DESCRIPTION

The following disclosure describes variable guide vanes (VGVs), associated assemblies, gas turbine engines and methods. In some embodiments, the VGVs described herein may allow for an expanded range of motion for VGVs and consequently may allow VGVs to adopt more aggressive vane angles. Relatively aggressive vane angles of VGVs may be desirable in some operating conditions of gas turbine engines such as at lower power outputs and/or when idling. In some embodiments, a VGV as described herein may include a button of the VGV that is configured to provide additional clearance between adjacent VGVs to widen spatial constraints and allow for adjacent (i.e., neighboring) VGVs to adopt relatively aggressive vane angles without colliding with each other.

The terms “connected” and “coupled” may include both direct connection/coupling (in which two elements contact each other) and indirect connection/coupling (in which at least one additional element is located between the two elements).

The terms “substantially” and “generally” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

Aspects of various embodiments are described through reference to the drawings.

FIG. 1 is a schematic axial cross-section view of an exemplary reverse flow turboprop gas turbine engine 10 comprising one or more VGVs 12 , as described herein. Even though the following description and FIG. 1 specifically refer to a turboprop gas turbine engine as an example, it is understood that aspects of the present disclosure may be equally applicable to other types of gas turbine engines including turboshaft and turbofan gas turbine engines. Gas turbine engine 10 may be of a type preferably provided for use in subsonic flight to drive a load such as propeller 14 via low-pressure shaft 16 (sometimes called “power shaft”) coupled to low-pressure turbine 18 . Propeller 14 may be coupled to low-pressure shaft 16 via a speed-reducing gearbox (not shown) in some embodiments. Low-pressure turbine 18 and low-pressure shaft 16 may be part of a first spool of gas turbine engine 10 known as a low-pressure spool. Gas turbine engine 10 may comprise a second or high-pressure spool comprising high-pressure turbine 20 , (e.g., multistage) compressor 22 and high-pressure shaft 24 .

Compressor 22 may draw ambient air into engine 10 via annular radial air inlet duct 26 , increase the pressure of the drawn air and deliver the pressurized air to combustor 28 where the pressurized air is mixed with fuel and ignited for generating an annular stream of hot combustion gas. High-pressure turbine 20 may extract energy from the hot expanding combustion gas and thereby drive compressor 22 . The hot combustion gas leaving high-pressure turbine 20 may be accelerated as it further expands, flows through and drives low pressure turbine 18 . The combustion gas may then exit gas turbine engine 10 via exhaust duct 30 .

In some embodiments, VGVs 12 may be suitable for installation in a core gas path 32 of engine 10 . For example, VGVs 12 may be variable inlet guide vanes disposed upstream of compressor 22 . Alternatively, VGVs 12 may instead be disposed between two rotor stages of compressor 22 . Gas path 32 may have a substantially annular shape and may have central axis A, which may correspond to a central axis of engine 10 , and may also correspond to an axis of rotation of a spool including compressor 22 . A plurality of VGVs 12 may be angularly distributed within annular gas path 32 and about central axis A. In other words, the plurality of VGVs 12 may be arranged to define a circular array of VGVs 12 within the annular gas path 32 . VGVs 12 may have a controllably variable orientation that may be controlled via a controller of engine 10 based on operating parameters of engine 10 . In some embodiments, the orientation of VGVs 12 may be synchronously varied via a unison ring or via another suitable drive mechanism.

FIGS. 2 A and 2 B are schematic representations of one VGV 12 at different orientations relative to central axis A and also relative to fluid flow F in annular gas path 32 . FIG. 2 A shows a situation where VGV 12 is aligned with central axis A. In other words, a chord C of VGV 12 may be substantially parallel with central axis A. This orientation of VGV 12 may correspond to a reference (e.g., zero) orientation where vane angle α equals 0. In this situation, annular gas path 32 may be substantially wide open and VGVs 12 may provide relatively little influence on flow F at the current angle of incidence with flow F.

FIG. 2 B shows a situation where VGV 12 is oriented at a non-zero vane angle α where VGV 12 is oriented obliquely to central axis A and to the general direction of flow F. In this situation, the effective area of annular gas path 32 may be reduced by the orientation of the cooperating plurality of VGVs 12 in comparison with that of FIG. 2 A . VGVs 12 may also provide a greater influence on flow F in this orientation. VGVs 12 may be rotatable within a range of orientations (e.g., vane angle α). In some embodiments, VGVs 12 may be rotatable in one or both directions from the zero angular position of FIG. 2 A so that vane angles α may be positive or negative relative to central axis A for example. In some embodiments, the range of orientations of VGVs 12 may be symmetric or asymmetric about the zero position. For example, VGVs 12 may be rotatable to a more aggressive vane angle α in one direction than in the opposite direction.

FIG. 3 is a tridimensional view of two exemplary adjacent VGVs 12 A, 12 B rotatably mounted to shroud 34 . Shroud 34 may be a radially-inner shroud ring relative to annular gas path 32 . Shroud 34 may include shroud surface 36 defining part of a radially-inner boundary of annular gas path 32 . VGV 12 A may include airfoil 38 A mounted to button 40 A. Airfoil 38 A may interact with fluid flow F inside of gas path 32 and may include leading edge 42 A and trailing edge 44 A. Airfoil 38 A and button 40 A may be rotatable as a unit about vane axis VA. Vane axis VA may be oriented partially radially or substantially entirely radially relative to central axis A. Airfoil 38 A may be integrally formed (e.g., cast, machined) with button 40 A or may be separately formed and attached to button 40 A by welding for example. Button 40 A may define a platform for VGV 12 A and may include platform surface 46 A for facing gas path 32 and defining part of gas path 32 adjacent airfoil 38 and at a radial extremity of airfoil 38 A. Platform surface 46 A may include depression 48 A for receiving therein part (e.g., a trailing edge) of an adjacent VGV 12 . Depression 48 A may define a sunken (e.g., concave, recessed) portion of platform surface 46 A that is lower than a surrounding portion of platform surface 46 A outside of depression 48 A. Button 40 A may be received in receptacle 50 A formed in shroud 34 . Receptacle 50 A may formed in shroud surface 36 and open to gas path 32 .

In some embodiments, VGV 12 B may, but not necessarily, be substantially identical to VGV 12 A and may be angularly offset from VGV 12 A in gas path 32 relative to central axis A. Only two VGVs 12 A, 12 B are shown in FIG. 3 but it is understood that more than two VGVs 12 A, 12 B may be circumferentially distributed around shroud 34 and installed in respective receptacles. Receptacle 50 C is shown without a VGV installed therein to show an exemplary internal configuration of receptacle 50 C. VGV 12 B may include airfoil 38 B mounted to button 40 B. Airfoil 38 B may interact with fluid flow F inside of gas path 32 and may include leading edge 42 B and trailing edge 44 B. Airfoil 38 B and button 40 B may be rotatable as a unit about vane axis VB. Vane axis VB may be oriented partially radially or substantially entirely radially relative to central axis A. Button 40 B may include platform surface 46 B including depression 48 A for receiving therein part (e.g., trailing edge 44 A) of VGV 12 A.

FIG. 3 shows shroud 34 being a radially-inner shroud of annular gas path 32 and buttons 40 A, 40 B being disposed at radially-inner ends of their respective VGVs 12 A, 12 B. However, it is understood that aspects of this disclosure may also be applied to a radially-outer shroud and to buttons disposed at radially outer ends of their respective VGVs 12 A, 12 B. For examples, depressions 48 A, 48 B or other types of cut-outs or recesses could instead, or in addition, be incorporated in radially-outer buttons to provide additional clearance (i.e., prevent interference) between adjacent VGVs 12 A, 12 B.

FIG. 4 is an enlarged tridimensional view of buttons 40 A, 40 B of VGVs 12 A, 12 B shown in FIG. 3 . VGS 12 A, 12 B may be rotatable within a range of vane angles α including a first orientation (e.g., α=0 as shown in FIG. 2 A ) where a part (e.g., trailing edge 44 A) of airfoil 38 A of VGV 12 A is outside of depression 48 B of platform surface 46 B of VGV 12 B. The range of vane angles α may include a more aggressive orientation, as shown in FIG. 4 , where the part (e.g., trailing edge 44 A) of airfoil 38 A of VGV 12 A is received inside depression 48 B of platform surface 46 B of VGV 12 B.

The presence of depression 48 B may allow part of airfoil 38 A to radially overlap button 40 B and thereby provide additional clearance to expand the range of orientations of VGV 12 A without interference between VGV 12 A and VGV 12 B. In other words, at the orientation of VGV 12 A shown in FIG. 4 , part of airfoil 38 A may be permitted to overlap a (e.g., partially circular) periphery of button 40 B when viewed along vane axis VB. Fillets 52 A, 52 B may be respectively disposed at junctions of airfoils 38 A, 38 B with respective buttons 40 A, 40 B.

FIG. 5 is a schematic side view of VGV 12 B. In some embodiments, VGV 12 A may have a substantially identical construction as VGV 12 B. Button 40 B may have leading end 54 B and trailing end 56 B. Leading end 54 B may be a foremost region of button 40 B toward oncoming fluid flow F when the vane angle α of VGV 12 B is at the zero orientation shown in FIG. 2 A . In other words, leading end 54 B of button 40 B may be disposed at an angular position corresponding to an angular position of leading edge 42 B of airfoil 38 B relative to vane axis VB. Trailing end 56 B may be diametrically opposed to leading end 54 B and may be a rearmost region of button 40 B in relation to the oncoming fluid flow F.

Depression 48 B may define a sunken portion of platform surface 46 B that is lower than a leading end portion 58 B of platform surface 46 B at or adjacent leading end 54 B of button 40 B. In some embodiments, some of platform surface 46 B outside of depression 48 B may be substantially flush with shroud surface 36 when vane angle α of VGV 12 B is at the zero orientation shown in FIG. 2 A . Accordingly, platform surface 46 B and shroud surface 36 may cooperatively define a relatively smooth boundary of gas path 32 with little discontinuity for interacting with fluid flow F when vane angle α of VGV 12 B is at the zero orientation.

Shroud surface 36 may be non-parallel to central axis A in some embodiments. For example, shroud surface 36 may be oriented obliquely to central axis A depending on the location of VGV 12 B along gas path 32 . In some embodiments, button 40 B may have a non-uniform (e.g., tapered) configuration where a thickness T 1 at leading end 54 B of button 40 B may be greater than a thickness T 2 at trailing end 56 B. The specific configuration of button 40 B may depend on the orientation of shroud surface 36 and also the orientation of vane axis VB so that some or a majority of platform surface 46 B may be substantially flush with shroud surface 36 .

Depression 48 B may have location D of maximum depth relative to one or more portion(s) of platform surface 46 B outside of depression 48 B. Location D of depression 48 B may also be below shroud surface 36 . Depression 48 B may be disposed closer to leading end 54 B of button 40 B than to trailing end 56 B of button 40 B along central axis A. Also, location D of maximum depth may be disposed closer to leading end 54 B of button 40 B than to trailing end 56 B of button 40 B along central axis A. At location D of depression 48 B, button 40 B may have a thickness T 3 . In some embodiments, thickness T 1 of button 40 B at leading end 54 B may be greater than thickness T 3 . In some embodiments, thickness T 3 may be greater than thickness T 2 of button 40 B at trailing end 56 B. As shown in FIG. 5 , thicknesses T 1 , T 2 and T 3 may be measured along a direction substantially parallel to vane axis VB.

FIG. 6 A is an enlarged tridimensional view of an exemplary button 140 of VGV 112 without depression 48 B formed therein showing a reference/baseline geometry of platform surface 146 of button 140 to which airfoil 138 may be mounted. VGV 112 may have a construction substantially identical to VGV 12 A except for the lack of depression 48 B. Like elements are identified using reference numerals that have been incremented by 100. Depending on the process selected for manufacturing VGV 12 B, VGV 112 may, in some embodiments, be a precursor to VGV 12 B before the forming (e.g., machining) of depression 48 B into button 140 .

FIG. 6 B is an enlarged tridimensional view of button 40 B in isolation showing depression 48 B formed in platform surface 46 B. Depression 48 B may have a concave shape facing gas path 32 (shown in FIG. 5 ). Depression 48 B may be disposed outside of fillet 52 B defined at the junction of button 40 B and airfoil 38 B. Depression 48 B may include a periphery of button 40 B (i.e., be radially outwardly open) to permit part of VGV 12 A to laterally enter depression 48 B and overlap button 40 B at larger (i.e., more aggressive) vane angles α. For example, location D of maximum depth may be disposed at or near a periphery of button 40 B. Accordingly, the depth of depression 48 B may gradually increase toward the periphery of button 40 B.

In some embodiments, depression 48 B may have a generally streamlined/contoured overall shape to provide favorable aerodynamic conditions. The shape, size and location of depression 48 B may be selected based on spatial constraints and the clearance desired for specific applications and vane geometries. For example, depression 48 B may include one or more transition surfaces 60 B that provide smooth/blended transitions with surrounding portion(s) of platform surface 46 B disposed outside of depression 48 B. In some embodiments, transition surface 60 B may provide a fillet surface blend with a portion of platform surface 46 B disposed outside of depression 48 B. In some embodiments, transition surface 60 B may provide a tangent-continuous type of surface continuity with a portion of platform surface 46 B disposed outside of depression 48 B. In some embodiments, transition surface 60 B may provide a curvature-continuous type of surface continuity with a portion of platform surface 46 B disposed outside of depression 48 B. In some embodiments, transition surface 60 B may provide such type(s) of surface continuity with leading end portion 58 B of platform surface 46 B at or adjacent leading end 54 B of button 40 B.

FIG. 7 is a schematic top view of VGV 12 B. Depression 48 B may be disposed in a forward left quadrant of button 40 B. In some embodiments, depending on the range of orientation of VGVs 12 , a second depression 48 B may be disposed in an opposite forward right quadrant of button 40 B. Both depressions 48 B may be mirror images of each other or may be of different shapes and sizes depending on the clearance requirements on each side of airfoil 38 B.

Depression 48 B may be angularly offset from leading end 54 B of button 40 B relative to vane axis VB extending normal to the page in FIG. 7 . Accordingly, in some embodiments, leading end 54 B of button 40 B may be devoid of any part of depression 48 B. In other words, leading end 54 B of button 40 B may be outside of depression 48 B. A location D of maximum depth of depression 48 B may be angularly offset from leading end 54 B of button 40 B. In some embodiments, location D of maximum depth of depression 48 B may be angularly offset from leading end 54 B by an angle β between 30 degrees and 60 degrees relative to vane axis VB for example.

As viewed along vane axis VB, button 40 B may have periphery P. In various embodiments, periphery P may be partially or entirely circular, or of another shape. For example, a majority of periphery P of button 40 B may be substantially circular. Part of periphery P at and near trailing end 56 B may be non-circular (e.g., linear). In some embodiments, leading edge 42 B of airfoil 38 B may be disposed within periphery P. In some embodiments, trailing edge 44 B of airfoil 38 B may be disposed outside of periphery P.

FIG. 8 is a flowchart of a method 100 of operating VGVs 12 A, 12 B described herein or using other VGVs. Aspects of method 100 may be combined with aspects of VGVs 12 A, 12 B and with other methods or actions disclosed herein. In various embodiments, method 100 may include:

rotating first and second VGVs 12 A, 12 B in (e.g., annular) gas path 32 (block 102 ); and

when rotating the first and second vanes, receiving part of VGV 12 A in depression 48 B formed in button 40 B of VGV 12 B.

In various embodiments, button 40 B may be disposed radially inwardly or radially outwardly of airfoil 38 B of VGV 12 B.

In reference to periphery P shown in FIG. 7 , the part (e.g., of trailing edge 44 A) of VGV 12 A may be disposed inside periphery P of button 40 B when the part of VGV 12 A is received in depression 48 B. In other words, the part (e.g., of trailing edge 44 A) of VGV 12 A may radially overlap platform surface 46 B of button 40 B when the part of VGV 12 A is received in depression 48 B.

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.